Scanning light-guiding encoder

ABSTRACT

The instant disclosure provides a scanning light-guiding encoder by forward focusing including a light-guiding grating wheel, a light-emitting module and an optical sensing module. The light-emitting module is surrounded by the light-guiding grating wheel. The optical sensing module includes a plurality of sensor elements adjacent to the light-guiding grating wheel, and a plurality of exposed sensor areas of the plurality of sensor elements are offset in the transverse direction and are arranged along a plurality of different horizontal lines parallel to each other.

BACKGROUND

1. Technical Field

The instant disclosure relates to an encoder, and in particular, to ascanning light-guiding encoder by forward focusing.

2. Description of Related Art

The monitors in the existing art use mice to move the location of thedata intended for processing. A mouse generally includes two sets of Xand Y axes encoders for outputting sequential logic signals (such as 11,10, 00, 01). The sequential logic signals are generated by abutting themouse against the table surface or other surfaces and moving the mousetoward specific directions, thereby moving a data location of themonitor to a different location. The principle of the use of a mouse isto generate a movement of a point on a plane by the operation of the Xand Y axis encoder. In other words, the operation of only one of the Xaxis encoder and the Y axis encoder only allows the movement of a pointon a line. The encoder generally includes a light-emitting module (suchas a light-emitting diode), a grating wheel (including blades) and anoptical sensing module. The grating wheel has a structure similar to amechanical gear which, when rotating, either shields the light generatedby the light-emitting module or allows the light to pass through. Whenthe light is shielded by the grating wheel, the optical sensing modulegenerates an OFF (0) signal; and when the light passes through thegrating wheel and is received by the optical sensing module, the opticalsensing module generates an ON (1) signal. The OFF (0) and ON (1)signals are sequentially generated and form a sequential signal. Forexample, when the grating wheel rotates clockwisely, the sequentialsignal generated by the optical sensing module can be a continuous andrepeated signal including 11, 10, 00, 01, 11, 10, 00, 01 . . . , andwhen the grating wheel rotates counter-clockwisely, the signalsgenerated can be 01, 00, 10, 11, 01, 00, 10, 11, 10 . . . . Thesesignals can be used in circuit cording.

Generally, the resolution (CPR, count per round) of the encoderincreases when the number of the blades increases and the distancebetween two sensors decreases. However, when the included angle betweentwo blades decreases, i.e., when the number of the blades increases, theouter diameter of the grating wheel increases. If the outer diameter ofthe grating wheel is fixed, when the number of the blades increases, thewidth of each of the blades decreases. However, due to the diffractionof the light, the extent that the width of the blades can be decreasedis also limited. Specifically, when the light passing the bladesdiffracts and is not shielded by the blades, the signals generated bythe two sensors of the optical sensing module will invariably be ON (1)signals, regardless of the rotating direction of the grating wheel.Therefore, the mouse is unable to generate different sequential signalsaccording to the movement thereof.

FIG. 1A is the schematic view of the arrangement of a light-guidingencoder of the existing art. FIG. 1B shows a partial view of the bladesof the light-guiding grating wheel 1 a and the optical sensing module 3a of the light-guiding encoder of the existing art. The light-guidingencoder of the existing art includes the light-guiding grating 1 a, alight-emitting module 2 a and the optical sensing module 3 a. In orderto overcome the problem related to the diffraction of light, the encoderemploys a light-guiding grating wheel 1 a having a plurality ofspherical surfaces S arranged continuously as a light-emitting surfacefor focusing the light emitted by the light-emitting module 3 a. Asshown in FIG. 1B, the optical sensing module 3 a includes the opticalsensing chips S1, S2 arranged on the same vertical axis. The lightemitted from the light-guiding grating wheel 1 a is focused at theoptical sensing chips S1, S2 of the optical sensing module 3 a.Specifically, the light-guiding grating wheel 1 a of the light-guidingencoder in the existing art can generate the signals of [1, 1], [0, 1],[1,0] and [0,0] upon rotating to the first position (1), the secondposition (2), the third position (3) and the fourth position (4)respectively. However, as shown in FIG. 1B, the light-guiding gratingwheel 1 a in the existing art has to employ two blades for generating aset of coding sequence including four signals.

In sum, since the width of the light beam decreases after passing thespherical surfaces due to the focusing principle, the distance betweenthe optical sensing module 3 a and the light-guiding grating wheel 1 aneeds to be controlled to ensure that the light is received by theoptical sensing module 3 a, thereby generating the signal. In addition,in the existing art, the optical sensing chips S1, S2 of the opticalsensing module 3 a are arranged along a same vertical axis, and hence,the light-guiding grating wheel 1 a employs two blades to complete acoding sequence [1,1], [0, 1], [1, 0] and [0, 0]. Therefore, theresolution of the light-guiding encoder cannot be significantlyimproved.

Therefore, there is a need in the art for improving the resolution ofthe light-guiding encoder while not increasing the dimension of thegrating wheel and the number of the blades.

SUMMARY

An embodiment of the instant disclosure provides scanning light-guidingencoder by forward focusing, comprising a light-guiding grating wheel, alight-emitting module and an optical sensor module. The light-emittingmodule surrounded by the light-guiding grating wheel. The optical sensormodule includes a plurality of sensor elements adjacent to thelight-guiding grating wheel. A plurality of exposed sensing areas of theplurality of sensor elements are offset in a transverse direction andare arranged along a plurality of different horizontal lines parallel toeach other.

Another exemplary embodiment of the instant disclosure provides scanninglight-guiding encoder by forward focusing comprising a light-guidinggrating wheel, a light-emitting module and an optical sensing module.The light-guiding grating wheel includes a light-guiding body and agear-like structure, in which the gear-like structure has a plurality ofaspherical projections. The light-emitting module is surrounded by thelight-guiding grating wheel. The optical sensing module is adjacent tothe light-guiding grating wheel. An incident light generated by thelight-emitting module passes through the light-guiding grating wheel forforming a parallel light or a near parallel light projected onto theoptical sensing module. A width of the parallel light or the nearparallel light is variable in accordance with a curvature of a topcurved surface of the aspherical projections.

Another exemplary embodiment of the instant disclosure provides ascanning light-guiding encoder by forward focusing comprising alight-guiding grating wheel, a light-emitting module and an opticalsensor module. The light-guiding grating wheel includes a light-guidingbody and a gear-like structure, in which the gear-like structure has aplurality of projections. The light-emitting module is surrounded by thelight-guiding grating wheel. The optical sensing module is adjacent tothe light-guiding grating wheel. A width of each of the projections ofthe gear-like structure is equal to a width of the optical sensingmodule.

The advantage of the instant disclosure is that the scanninglight-guiding encoder by forward focusing employs the design of “each ofthe sensor elements has an exposed sensing area, and the plurality ofexposed sensing areas of the plurality of sensor elements are offset inthe transverse direction and are arranged along a plurality of differenthorizontal lines parallel to each other”, and hence, the parallel lightor near parallel light projected onto the optical sensing module cancooperate with the exposed sensing areas of the plurality of sensorelements. Therefore, the resolution of the encoder can be improvedwithout increasing the dimension of the light-guiding grating wheel andthe number of the blades. In addition, the optical scanninglight-guiding encoder can prevent the diffraction of light passing thelight-guiding grating wheel.

In order to further understand the techniques, means and effects of theinstant disclosure, the following detailed descriptions and appendeddrawings are hereby referred to, such that, and through which, thepurposes, features and aspects of the instant disclosure can bethoroughly and concretely appreciated; however, the appended drawingsare merely provided for reference and illustration, without anyintention to be used for limiting the instant disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the instant disclosure, and are incorporated in andconstitute a part of this specification. The drawings illustrateexemplary embodiments of the instant disclosure and, together with thedescription, serve to explain the principles of the instant disclosure.

FIG. 1A is a schematic view of the arrangement of a light-guidingencoder of the existing art;

FIG. 1B is a schematic view of the generation of a coding sequenceperformed by the light-guiding encoder of the existing art;

FIG. 2 is a schematic view of the arrangement of an scanninglight-guiding encoder by forward focusing provided by an embodiment ofthe instant disclosure;

FIG. 3 is a schematic view of the arrangement of an scanninglight-guiding encoder by forward focusing provided by another embodimentof the instant disclosure;

FIG. 4 is a schematic view of the arrangement of an scanninglight-guiding encoder by forward focusing provided by yet anotherembodiment of the instant disclosure;

FIG. 5 is a schematic view of a light path of a parallel light or a nearparallel light of the scanning light-guiding encoder by forward focusingprovided by an embodiment of the instant disclosure;

FIG. 6 is a three-dimensional view of a light-guiding grating wheel ofthe scanning light-guiding encoder by forward focusing provided by anembodiment of the instant disclosure;

FIG. 7 is an enlarged view of part A in FIG. 6;

FIG. 8 is a fragmentary schematic view of a gear-like structure of alight-guiding encoder;

FIG. 9 is a fragmentary view of a gear-like structure of the scanninglight-guiding encoder by forward focusing provided by an embodiment ofthe instant disclosure;

FIG. 10 is a fragmentary sectional view of the structure shown in FIG.7;

FIG. 11 is another fragmentary sectional view of the structure shown inFIG. 7;

FIG. 12 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by a first embodimentof the instant disclosure rotates to a first position;

FIG. 13 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by the firstembodiment of the instant disclosure rotates to a second position;

FIG. 14 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by the firstembodiment of the instant disclosure rotates to a third position;

FIG. 15 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by the firstembodiment of the instant disclosure rotates to a fourth position;

FIG. 16 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by a secondembodiment of the instant disclosure rotates to a first position;

FIG. 17 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by the secondembodiment of the instant disclosure rotates to a second position;

FIG. 18 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by the secondembodiment of the instant disclosure rotates to a third position;

FIG. 19 is a fragmentary schematic view showing the relationship betweenthe parallel light or the near parallel light and the optical sensingmodule when the light-guiding grating wheel of the scanninglight-guiding encoder by forward focusing provided by the secondembodiment of the instant disclosure rotates to a fourth position;

FIG. 20 is a schematic view of the signal generated by the grating andthe optical sensing module of the scanning light-guiding encoder byforward focusing provided by the second embodiment of the instantdisclosure;

FIG. 21 is a fragmentary schematic view of the relationship between theparallel light or the near parallel light and the optical sensing modulewhen the light-guiding grating wheel of the scanning light-guidingencoder by forward focusing provided by the third embodiment of theinstant disclosure rotates to a first position;

FIG. 22 is a schematic view of the signal generated by the opticalsensing module shown in FIG. 21;

FIG. 23 is a fragmentary schematic view of the relationship between theparallel light or the near parallel light and the optical sensing modulewhen the light-guiding grating wheel of the scanning light-guidingencoder by forward focusing provided by the fourth embodiment of theinstant disclosure rotates to a first position; and

FIG. 24 is a schematic view of the signal generated by the opticalsensing module shown in FIG. 23.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of theinstant disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

Referring to FIG. 2 to FIG. 4, the scanning light-guiding encoder byforward focusing E includes a light-guiding grating wheel 1, alight-emitting module 2 and an optical sensing module 3. Thelight-guiding grating wheel 1 can have a single-layer or a multi-layerstructure, i.e., a plurality of light-guiding grating wheels 1 stackedone above another can be used in the instant disclosure. As shown inFIG. 2, in an embodiment, the light-emitting module 2 is surrounded bythe light-guiding grating wheel 1, and the light-emitting module 2 andthe optical sensing module 3 are disposed on a same straight line. Inaddition, as shown in FIG. 2 to FIG. 4, the scanning light-guidingencoder by forward focusing E provided by the embodiments of the instantdisclosure can further include a grating 4 disposed between thelight-guiding grating wheel 1 and the optical sensing module 3. Thegrating 4 is an optional component. The differences between FIG. 2, FIG.3 and FIG. 4 reside in the structure of the light-guiding grating wheel1. The details of the light-guiding grating wheel 1 and the embodimentsthereof are described later.

Referring to FIG. 5, the scanning light-guiding encoder by forwardfocusing E provided by the instant disclosure can further include areflected mirror 5. The reflecting mirror 5 is disposed on a side of thelight-guiding grating wheel 1 for reflecting the parallel light or thenear-parallel light P from the light-guiding grating wheel 1 to pass thegrating 4, then emit toward the optical sensing module 3.

Reference is now made to FIG. 6 and FIG. 7. The light-guiding gratingwheel 1 of the scanning light-guiding encoder by forward focusing E ismade of light-guiding materials. For example, the light-guiding gratingwheel 1 can be made of glass, acylic, polycarbonate (PC), or anycombination thereof. However, the material of the light-guiding gratingwheel 1 is not limited in the instant disclosure.

The light-guiding grating wheel 1 includes a light-guiding body 101 andan outer gear-like structure 102 disposed on the outer surroundingsurface of the light-guiding body 101. The inner surrounding surface ofthe light-guiding body 101 is an annular light-receiving surface 11. Thegear-like structure 102 has an annular light-output surface 13 formed ofa plurality of aspherical surfaces 130 (or spherical surfaces) connectedsequentially. The outer gear-like structure 102 is formed by a pluralityof aspherical projections 1020 connected sequentially. In the instantdisclosure, the plurality of aspherical projections 1020 can besubstituted with spherical projections. Specifically, the annularlight-receiving surface 11 facing the light-emitting module 2 is usedfor receiving light emitted by the light-emitting module 2.

As shown in FIG. 7, the annular light-output surface 13 is formed by aplurality of aspherical surfaces 130 connected sequentially. Each of theaspherical surfaces 130 has two reflecting surfaces 13 a and alight-output surface 13 b connected between the two reflecting surfaces13 a. The reflecting surfaces 13 a can be reflecting plane surfaces, andthe light-output surface 13 b is an aspherical light-output surface suchas hyperboloid, a paraboloid or ellipsoid light-output surfaces.

Referring to FIGS. 8 and 9, the light-guiding encoder generally employsa spherical structure S having a center of sphere to constitute thelight-emitting surface of the grating wheel in an encoder. The lightemits from the spherical structure S and projects onto a sensor.However, since the spherical structure S focuses light, the light beamemitted from the spherical structure S is focused and has differentwidths at different positions.

Different from the spherical structure of a conventional light-guidingencoder, the aspherical structure A shown in FIG. 9 does not have acenter of sphere but has a principle axis. A light beam emitted from theaspherical structure A (such as a paraboloid) will be a parallel lightor a near parallel light which is substantially a parallel light. Theembodiments of the instant disclosure employ the aspherical structure Asuch as hyperboloid or paraboloid to constitute the light-output surface13 b. Therefore, the annular light-output surface 13 having theaspherical surface 130 can maintain the width W of the light beamleaving the light-guiding grating wheel 1 through the annularlight-output surface 13. The parallel light or near parallel lighthaving a constant width W can cooperate with the optical sensingelements or exposed optical sensing areas having specific arrangementfor obtaining coding signals with improved resolution. To be specific,since the light beam leaving the light-guiding grating wheel 1 has aconstant width W, the resolution of the scanning light-guiding encoderby forward focusing E can be effectively improved by controlling thesize and arrangement of the optical sensing element and exposed sensingarea of the optical sensing module 3, and the size of the asphericalsurface 130 of the optical sensing module 3. The details regarding thecooperation between the annular light-output surface 13 and the exposedsensing areas of the optical sensing elements in the optical sensingmodule 3 will be described later.

As shown in FIG. 10, each of the aspherical surfaces 130 can have afirst surface a₁, a second surface a₂, a third surface a₃ and a fourthsurface a₄ connected sequentially. Each of the first surface a₁ and thefourth surface a₄ is a reflecting surface 13 a, and the second surfacea₂ and the third surface a₃ connected between the first surface a₁ andthe fourth surface a₄ together form a light-output surface 13 b. In theinstant disclosure, since the incident angle of the reflected light Rprojected onto the reflecting surface 13 a is equal to the reflectingangle thereof, the reflected light R is reflected and emits toward theinner portion of the light-guiding grating wheel 1. Therefore, thelight-output surface 13 b (i.e., the second surface a₂ and the thirdsurface a₃) is the part in the annular light-output surface 13 thatallows the reflected light R to pass through. The reflected light Rpasses through the light-output surface 13 b and forms the parallellight or near-parallel light P. On the other hand, if the reflectedlight R emits toward the reflecting surface 13 a (i.e., the firstsurface a₁ or the fourth surface a₄) in the annular light-output surface13, the reflected light R will not be able to pass directly through thelight-guiding grating wheel 1. It should be noted that the width of theparallel light or the near parallel light passing the annularlight-output surface 13 can be equal to the width of each of theaspherical projections 1020. However, the instant disclosure is notlimited thereto.

In addition, the first surface a₁, the second surface a₂, the thirdsurface a₃ and the fourth surface a₄ can have a same area of verticalprojection. In other words, as shown in FIG. 10, the first surface a₁,the second surface a₂, the third surface a₃ and the fourth surface a₄can have the same projection width d. Under this circumstance, thesecond surface a₂ and the third surface a₃ constituting the light-outputsurface 13 b have a projection width that is half of the totalprojection width. However, the arrangement of the first surface a₁, thesecond surface a₂, the third surface a₃ and the fourth surface a₄ can beadjusted according to actual needs. By adjusting the curvature of thelight-output surface 13 b, the width of the parallel light ornear-parallel light P leaving the light-guiding grating wheel 1 can beadjusted. In other words, the width of the parallel light ornear-parallel light P is variable in accordance to the curvature of thetop surface of the aspherical projection 1020.

Referring to FIG. 11, the reflecting light R projects onto thereflecting surface 13 a (the first surface a₁ shown in FIG. 10) and isreflected to emit toward the light-output surface 13 b (the secondsurface a₂ and the third surface a₃). Afterward, the reflecting light Remits from the aspherical surface 130 of the light-output surface 13 bas the parallel light or the near-parallel light P.

based on the above design, when the light-guiding grating wheel 1rotates, the reflected light R of the embodiments of the instantdisclosure can be reflected by a part of the corresponding asphericalsurface 130 (the reflecting surfaces 13 a), or, the reflected light Rcan pass through a part of the aspherical surface 130 (the light-outputsurface 13 b) and form the parallel light or near-parallel light P. Theparallel light or near-parallel light P can pass through the grating 4and project onto the optical sensing module 3, thereby forming a circuitcoding signal with high resolution.

It should be noted that the light-guiding grating wheel 1 provided bythe embodiments of the instant disclosure can have different structuraldesigns. Reference is made to FIG. 3 and FIG. 4. As shown in FIG. 3, thelight-guiding grating wheel 1 can includes the light-guiding body 101and the inner gear-like structure 103 disposed on the inner surroundingsurface of the light-guiding body 101. The outer surrounding surface ofthe light-guiding body 101 is the annular light-output surface 13. Theinner gear-like structure 103 has the annular light-receiving surface 11formed by a plurality of aspherical surfaces 110 connected sequentiallyand having a principal axis. The inner gear-like structure 103 is formedby a plurality of aspherical projections 1030 connected sequentially.The incident light L generated by the light-emitting module 2 enters thelight-guiding grating wheel 1 through the annular light-receivingsurface 11 of the inner gear-like structure 103 and passes through theannular light-output surface 13 to form the parallel light or thenear-parallel light P projected onto (or “forward focused on”) theoptical sensing module 3.

In another embodiment, the light-guiding grating wheel 1 as shown inFIG. 4 includes the light-guiding body 101, the outer gear-likestructure 102 disposed on the outer surrounding surface of thelight-guiding body 101 and the inner gear-like structure 103 disposed onthe inner surrounding surface of the light-guiding body 101. The outergear-like structure 102 has the annular light-output surface 13 formedby a plurality of aspherical projections 1030 connected sequentially.The outer gear-like structure 102 is formed by a plurality of asphericalprojections 1020 connected sequentially. The inner gear-like structure103 has an annular light-receiving surface 11 formed by a plurality ofaspherical surfaces 110 connected sequentially and having a principalaxis, and the inner gear-like structure 103 is formed by a plurality ofaspherical projections 1030 connected sequentially. The incident light Lgenerated by the light-emitting module 2 enters the light-guidinggrating wheel 1 through the annular light-receiving surface 11 of theinner gear-like structure 103 and passes through the annularlight-output surface 13 of the outer gear-like structure 102 to form theparallel light or the near-parallel light P projected onto the opticalsensing module 3.

Regarding the light-guiding wheels 1 shown in FIG. 3 and FIG. 4, similarto the aspherical surfaces 130 of the annular light-output surface 13,the aspherical surfaces 110 of the annular light-receiving surface 11can has two reflecting surfaces and a light-output surface connectedbetween the two reflecting surfaces. In addition, the reflectingsurfaces can be reflecting planes and the light-output surface can be anaspherical surface such as a hyperboloid, a paraboloid or ellipsoidlight-output surfaces. Therefore, the annular light-receiving surface 11can generate an optical effect similar to the annular light-outputsurface 13.

Reference is made to FIG. 2. The light-emitting module 2 is surroundedby the annular light-receiving surface 11 for generating an incidentlight L emitting toward the annular light-receiving surface 11. Forexample, the light-emitting module 2 can be at least a light-emittingdiode. However, the implementation of the light-emitting module 2 is notlimited thereto.

As shown in FIG. 2, the optical sensing module 3 can be disposed besidethe annular light-output surface 13 for receiving the parallel light ornear-parallel light P passing through the light-output surface 13 b inthe aspherical surface 130 of the annular light-output surface 13. Inanother implementation, as shown in FIG. 5, the optical sensing module 3can be disposed at a side near the annular light-receiving surface 11 ofthe light-guiding grating wheel 1, and a reflecting mirror 5 is employedto reflect the parallel light or near-parallel light P emitted from thelight-output surface 13 b in the aspherical surface 130 of the annularlight-output surface 13.

The implementation of the optical sensing module 3 is variable inaccordance to the presence of the grating 4. For example, when thescanning light-guiding encoder by forward focusing E does not include agrating 4, the optical sensing module 3 includes a plurality of sensingelements for receiving the parallel light or near-parallel light Pemitted from the aspherical surface 130. Specifically, the sensingelements of the optical sensing module 3 having specific dimensions arearranged in a specific manner on the surface of the optical sensingmodule 3 for cooperating with the aspherical surface 130 of thelight-guiding grating wheel 1 to generate signals. In an implementationwithout the grating 4, the plurality of sensing elements are offset inthe transverse direction and are arranged along a plurality of differenthorizontal lines parallel to each other.

When the scanning light-guiding encoder by forward focusing E includesthe grating 4, the grating 4 is disposed between the light-guidinggrating wheel 1 and the optical sensing module 3, and includes aplurality of slit-like openings. The optical sensing module 3 has aplurality of strip-like sensing elements. The openings expose specificareas of the sensing elements for forming a plurality of exposed sensingareas of the optical sensing module 3.

In order to improve the resolution of the scanning light-guiding encoderby forward focusing E, the width of the plurality of sensing elementsand the exposed sensing areas of the sensing elements must be controlledto cooperate with the width of the aspherical projections 1020 or 1030of the light-guiding grating wheel 1 and the width of the light-outputsurface 13 b. Therefore, the scanning light-guiding encoder by forwardfocusing E provided by the embodiments of the instant disclosure allowsthe optical sensing module 3 to generate a complete coding sequence by asingle aspherical projection 1020 or 1030 (for example, the signals[0,0], [0,1], [1,0] and [1,1] can be generated by a single asphericalprojection 1020 or 1030). The details of the technical means will bedescribed later.

In the instant disclosure, the number of sensing elements and exposedsensing areas of the optical sensing module 3 can be adjusted accordingto actual needs. For example, as shown in FIG. 12 to FIG. 15, theoptical sensing module 3 includes a first sensing element 31′ and asecond sensing element 32′ parallel to each other for receiving theparallel light or near-parallel light P emitted from the annularlight-output surface 13. The signals [0,0], [0,1], [1,0] and [1,1] canbe generated in accordance to the receiving status of the parallel lightor near-parallel light P. In other words, two sensing elements cangenerate 2² signals. In addition, as shown in FIG. 21 and FIG. 23, theoptical sensing module 3 can also include three or four sensingelements, and each of the sensing elements has one or more exposedsensing areas exposed by the openings of the grating 4.

Furthermore, when the light-guiding grating wheel 1 rotates and theincident light L generated by the light-emitting module 2 enters thelight-guiding grating wheel 1 through the annular light-receivingsurface 11, the reflected light R passes through a part of thecorresponding aspherical surface 130 or 110 (i.e., the light-outputsurface 13 b) for forming the parallel light or near-parallel light Pafter passing the annular light-output surface 13, or is reflected bythe other part of the corresponding aspherical surface 130 or 110 (i.e.,the reflecting surface 13 a). Therefore, the parallel light ornear-parallel light P emitted from the light-guiding grating wheel 1 canbe received by the optical sensing module 3 for generating thesequential signals for circuit coding.

The operational details for generation of sequential signals by theoptical scanning light-guiding encoder E are provided below in theembodiments of the instant disclosure.

First Embodiment

Reference is made to FIG. 12 to FIG. 15 which show the relationshipbetween the parallel light or the near parallel light P and the opticalsensing module 3 when the light-guiding grating wheel 1 of the scanninglight-guiding encoder by forward focusing E provided by the firstembodiment of the instant disclosure rotates to different positions.

Specifically, as shown in FIG. 12, the optical sensing module 3 includesthe first sensing element 31′ and the second sensing element 32′ (bothof which is strip-like), and the two sensing elements have the samewidth D1 and are flushed at the two ends thereof to allow the opticalsensing module 3 to have the same width D1. The optical sensing module 3and the light-guiding grating wheel 1 have a grating 4 disposedtherebetween and having a width larger than D1. The grating 4 is forshielding specific areas of the first sensing element 31′ and the secondsensing element 32′ and exposing the reminder areas. The first opening41 and the second opening 42 of the grating 4 expose the first exposedsensing area 31 of the first sensing element 31′ and the second exposedsensing area 32 of the second sensing element 32′ respectively. In thisembodiment, the first exposed sensing area 31 and the second opening 42has a width of ¼ D1, and hence, the first exposed sensing area 31 andthe second exposed sensing area 32 also have a width of ¼ D1. The firstexposed sensing area 31 and the second exposed sensing area 32 areoffset in the traverse direction and are arranged along a plurality ofdifferent horizontal lines H1, H2 parallel to each other.

In embodiments of the instant disclosure, the width of the asphericalprojections 1020 is the same as the width D1 of the optical sensingmodule 3. Therefore, each of the aspherical surfaces 130 of thelight-guiding grating wheel 1 can correspond to the optical sensingmodule 3 having the first sensing element 31′ and the second sensingelement 32′ for generating a complete coding sequence by a singleaspherical surface 130. In addition, in the first embodiment, the widthW1 of the parallel light or near-parallel light P emitted from thelight-output surface 13 b is larger or equal to half of the width D1 ofthe optical sensing module 3, i.e., W1≥½ D1. The ratio of the width W1to the width D1 of the light-guiding grating wheel 1 of the embodimentshown in FIG. 12 to FIG. 15 is W1=½ D1. When the light-output surface 13b of the annular light-output surface 13 rotates to a locationcorresponding to the first exposed sensing area 31 and the secondexposed sensing area 32 (by the rotation of the light-guiding gratingwheel 1), i.e, the location shown in FIG. 14, the parallel light ornear-parallel light P can project onto the first exposed sensing area 31and the second exposed sensing area 32. Reference will now be made toFIG. 12 to FIG. 15 to show different states during the rotation of thelight-guiding grating wheel 1.

Referring to FIG. 12, the light-guiding grating wheel 1 rotates to afirst position. The first exposed sensing area 31 and the second exposedsensing area 32 of the optical sensing module 3 correspond to the fourthsurface a₄ of one of the aspherical surfaces 130 and the first surfacea₁ of the next aspherical surface 130 of the light-guiding grating wheel1 respectively. Since the first surface a₁ and the fourth surface a₄ areboth a reflecting surface 13 a, the reflected light R emitting towardthe first surface a₁ and the fourth surface a₄ is reflected by thereflecting surfaces 13 a. Therefore, the first exposed sensing area 31and the second exposed sensing area 32 corresponding to the fourthsurface a₄ and the first surface a₁ do not receive any optical signal,and hence, the optical sensing module 3 generates a [0,0] signal.

Referring next to FIG. 13, the light-guiding grating wheel 1 rotates toa second position. The first exposed sensing area 31 and the secondexposed sensing area 32 of the optical sensing module 3 correspond tothe first surface a₁ and the second surface a₂ of one of the asphericalsurfaces 130 of the light-guiding grating wheel 1. The first surface a₁is a reflecting surface 13 a, and hence, the reflected light R projectedonto the first surface a₁ is reflected to the inner portion of thelight-guiding grating wheel 1 and cannot leave the light-guiding gratingwheel 1 from the reflecting surface 13 a. The reflected light R emittingtoward the second surface a₂ passes through the aspherical surface 130and forms the parallel light or near-parallel light P. The parallellight or near-parallel light P emits toward the second exposed sensingarea 32 corresponding to the second surface a₂, and hence, the opticalsensing module 3 generates a [0,1] signal. In addition, although thereflected light R can pass through the third surface a₃ to form theparallel light or near-parallel light P emitting from the asphericalsurface 130, the third surface a₃ is not corresponded to any exposedsensing area of the optical sensing module 3 and is blocked by thegrating 4, and hence, this part of the parallel light or near-parallellight P does not contribute to the signal generated by the opticalsensing module 3.

Referring to FIG. 14, the light-guiding grating wheel 1 rotates to athird position. The first exposed sensing area 31 and the second exposedsensing area 32 of the optical sensing module 3 correspond to the secondsurface a₂ and the third surface a₃ of one of the aspherical surfaces130. The reflected light R emits toward the aspherical surface 130 andleaves the light-guiding grating wheel 1 through the light-outputsurface 13 b having the second surface a₂ and the third surface a₃. Theparallel light or near-parallel light P formed by the reflected light Rleaving the light-guiding grating wheel 1 emits toward the first exposedsensing area 31 and the second exposed sensing area 32 of the opticalsensing module 3, and hence, the optical sensing module 3 generates a[1,1] signal.

Referring to FIG. 15, the light-guiding grating wheel 1 rotates to afourth position. The first exposed sensing area 31 and the secondexposed sensing area 32 of the optical sensing module 3 correspond tothe third surface a₃ and the fourth surface a₄ of one of the asphericalsurfaces 130 respectively. The reflected light R emitting toward thethird surface a₃ passes through the third surface a₃ and forms theparallel light or near-parallel light P. The parallel light ornear-parallel light P is received by the first exposed sensing area 31.The fourth surface a₄ is a reflecting surface 13 a, and hence, thereflected light R directly emitting toward the fourth surface a₄ isreflected by the fourth surface a₄ and cannot leave the light-guidinggrating wheel 1 through the fourth surface a₄. Therefore, the secondexposed sensing area 32 corresponding to the fourth surface a₄ cannotreceive the optical signal of the parallel light or near-parallel lightP. When the light-guiding grating wheel 1 rotates to the fourthposition, the optical sensing module 3 generates a [1,0] signal.

As described above, when the light-guiding grating wheel 1 rotates todifferent positions, based on the design of the reflecting surface 13 aand the light-output surface 13 b in the aspherical surfaces 130 of theoptical sensing module 3, and more importantly, based on the design ofthe dimensions of the first exposed sensing area 31 and the secondexposed sensing area 32 in the optical sensing module 3 in cooperationwith the reflecting surface 13 a and the light-output surface 13 b, thelight-guiding grating wheel 1 can generate 2²=4 sensing signals by asingle aspherical surface 130, thereby significantly increasing theresolution of the scanning light-guiding encoder by forward focusing E.

Second Embodiment

Reference is next made to FIG. 16 to FIG. 20, in which FIG. 16 to FIG.19 are fragmentary schematic views showing the relationship between theparallel light or the near parallel light P and the optical sensingmodule 3 when the light-guiding grating wheel 1 of the scanninglight-guiding encoder by forward focusing E provided by a secondembodiment of the instant disclosure rotates to different positions,i.e., from the first position (1) to the fourth position (4). FIG. 20 isa schematic view of the signal generated by the optical sensing module 3in the second embodiment of the instant disclosure.

In FIG. 16 to FIG. 19, the first sensing element 31′ and the secondsensing element 32′ of the optical sensing module 3 have a first exposedsensing area 31 and a second exposed sensing area 32 exposed by thefirst opening 41 and the second opening 42 of the grating 4respectively. The first exposed sensing area 31 and the second exposedsensing area 32 are divided into a plurality of coding areas, and thewidth W2 of the parallel light or near-parallel light P is smaller thanor equal to the width of each coding area. Referring to FIG. 16, thefirst exposed sensing area 31 and the second exposed sensing area 32each includes two coding areas each having a width of ¼ D2.

In other words, in the second embodiments, the parallel light ornear-parallel light P emitted from the annular light-reflecting surface12 has a width W2 smaller or equal to ¼ of the width D3 of the opticalsensing module 3 having the first sensing element 31′ and the secondsensing element 32′, i.e., W2≤¼ D2. The ratio of the width W2 to thewidth D2 of the light-guiding grating wheel 1 of the embodiment shown inFIG. 16 to FIG. 19 is W2=¼ D2. In addition, in the present embodiment,the width of the first exposed sensing area 31 and the second exposedsensing area 32 is twice that of the width W2 of the parallel light ornear-parallel light P, i.e., the first exposed sensing area 31 and thesecond exposed sensing area 32 each has a width of ½ D2. Furthermore,the first exposed sensing area 31 and the second exposed sensing area 32are offset relative to each other, i.e., the first exposed sensing area31 and the second exposed sensing area 32 are offset for a distance of ¼D2 along the direction of the horizontal lines H1 and H2.

As shown in FIG. 16, the light-guiding grating wheel 1 rotates to afirst position (1). Neither the first exposed sensing area 31 nor thesecond exposed sensing area 32 corresponds to the second surface a₂ andthird surface a₃ which constitute the light-output surface 13 b andthrough which the parallel light or near-parallel light P is emitted.Therefore, as shown in FIG. 20, when the light-guiding grating wheel 1rotates to the first position (1), the optical sensing module 3 cannotreceive any optical signal and generates a [0,0] signal.

Referring to FIG. 17, the light-guiding grating wheel 1 rotates to asecond position (2). The first exposed sensing area 31 corresponds tothe first surface a₁ which is one of the reflecting surfaces 13 a in thelight-guiding grating wheel 1 and the fourth surface a₄ of the previousaspherical surface 130, and hence the first exposed sensing area 31cannot receive any optical signal. In addition, the parallel light ornear-parallel light P emitted from the second surface a₂ and the thirdsurface a₃ of the light-guiding grating wheel 1 emits toward the opticalsensing module 3 and is projected onto a part of the second exposedsensing area 32 exposed by the second opening 42. Therefore, as shown inFIG. 20, when the light-guiding grating wheel 1 rotates to the secondposition (2), the optical sensing module 3 generates a [0,1] signal.

Referring to FIG. 18, the light-guiding grating wheel 1 rotates to athird position (3). The parallel light or near-parallel light P emittedfrom the second surface a₂ and the third surface a₃ of the light-guidinggrating wheel 1 emits toward the optical sensing module 3 and projectsonto a part of the first exposed sensing area 31 exposed by the firstopening 41 and the second exposed sensing area 32 exposed by the secondopening 42. Therefore, as shown in FIG. 20, when the light-guidinggrating wheel 1 rotates to the third position (3), the optical sensingmodule 3 generates a [1,1] signal.

Referring to FIG. 19, the light-guiding grating wheel 1 rotates to afourth position (4). The parallel light or near-parallel light P emittedfrom second surface a₂ and the third surface a₃ emits toward the opticalsensing module 3 and projects onto a part of the first exposed sensingarea 31 exposed by the first opening 41. The second exposed sensing area32 is corresponded to the fourth surface a₄ which is one of thereflecting surfaces 13 a in the light-guiding grating wheel 1, and thefirst surface a₁ of the next aspherical surface 130. Therefore, thesecond exposed sensing area 32 cannot receive any optical signal.Therefore, as shown in FIG. 20, when the light-guiding grating wheel 1rotates to the fourth position (4), the optical sensing module 3generates a [1,0] signal.

As described above, when the light-guiding grating wheel 1 rotates todifferent positions, based on the design of the reflecting surface 13 aand the light-output surface 13 b in the aspherical surfaces 130 ofoptical sensing module 3, and more importantly, based on the design ofthe dimensions of the first exposed sensing area 31 and the secondexposed sensing area 32 in the optical sensing module 3 in cooperationwith the reflecting surface 13 a and the light-output surface 13 b, thelight-guiding grating wheel 1 can generate 2²=4 sensing signals.Specifically, by adjusting the width W2 of the parallel light ornear-parallel light P to be smaller than or equal to the ¼ of the widthD2 of the optical sensing module 3 having the first sensing element 31′and the second sensing element 32′ (each of the aspherical projections1020 also has a width D2), i.e., W2≤¼ D1, the resolution of the scanninglight-guiding encoder by forward focusing E can be improved.

Third Embodiment

Reference is next made to FIG. 21 and FIG. 22, which illustrate theschematic views of the scanning light-guiding encoder by forwardfocusing E of the third embodiment for generating coding signals.Specifically, FIG. 21 is a fragmentary schematic view of therelationship between the parallel light or the near parallel light andthe optical sensing module when the light-guiding grating wheel of theoptical scanning light-guiding encoder provided by the third embodimentof the instant disclosure rotates to a first position; and FIG. 22 is aschematic view of the signal generated by the optical sensing moduleshown in FIG. 21.

Different from the previous embodiments, the optical sensing module 3has a first sensing element 31′, a second sensing element 32′, a thirdsensing element 33′ and a fourth sensing element 34′ in the presentembodiment, each having the same width D3. The first opening 41, thesecond opening 42, the third opening 43 and the fourth opening 44 of thegrating 4 are used to expose the first exposed sensing area 31, thesecond exposed sensing area 32, the third exposed sensing area 33 andthe fourth exposed sensing area 34 which are offset from each other. Thefirst exposed sensing area 31, the second exposed sensing area 32, thethird exposed sensing area 33 and the fourth exposed sensing area 34 aredivided into a plurality of coding areas, and the width W3 of theparallel light or near-parallel light P is smaller than or equal to thewidth of each of the coding areas. Referring to FIG. 21, the aboveexposed sensing areas each includes four coding areas each having awidth of ⅛ D2.

In other words, in the present embodiment, the first exposed sensingarea 31, the second exposed sensing area 32, the third exposed sensingarea 33 and the fourth exposed sensing area 34 each has a width of ½ D3.In addition, the first exposed sensing area 31, the second exposedsensing area 32, the third exposed sensing area 33 and the fourthexposed sensing area 34 are offset from each other at a distance of ⅛ D3on different horizontal lines H1, H2, H3 and H4.

The width W3 of the parallel light or near-parallel light P emittingfrom the aspherical surface 130 is smaller than or equal to ⅛ of thewidth D3 of the optical sensing module 3, i.e., W3≤⅛ D3. The ratio ofthe width W3 to the width D3 of the light-guiding grating wheel 1 of theembodiment shown in FIG. 21 is W3=⅛ D3. Similar to the previousembodiments, the width of each of the aspherical projections 1020 is thesame as the width D3 of the optical sensing module 3. For example, inthe state shown in FIG. 21, the parallel light or near-parallel light Pprojects onto the optical sensing module 3 and allows the opticalsensing module 3 to generate a signal of [0,0,0,0]. In the thirdembodiment, the signal generated by the optical sensing module 3 inaccordance with the rotation position of the light-guiding grating wheel1 is shown in FIG. 22. Therefore, in the present embodiment, the opticalscanning light-guiding encoder E can generate 2³=8 signals.

Fourth Embodiment

Reference is next made to FIG. 23 and FIG. 24, in which FIG. 23 is afragmentary schematic view of the relationship between the parallellight or the near parallel light and the optical sensing module when thelight-guiding grating wheel of the optical scanning light-guidingencoder provided by the fourth embodiment of the instant disclosurerotates to a first position; and FIG. 24 is a schematic view of thesignal generated by the optical sensing module shown in FIG. 23.

Referring to FIG. 23, in the present embodiment, the optical sensingmodule 3 of the optical scanning light-guiding encoder E includes thefirst sensing element 31′, the second sensing element 32′ and the thirdsensing element 33′, which are strip-like and arranged parallel to eachother. The optical sensing module 3 having the first sensing element31′, the second sensing element 32′ and the third sensing element 33′has a width D4. The first openings 41 a-41 d of the grating 4 exposespecific areas of the first sensing element 31′ and form the firstexposed sensing areas 31 a-31 d; the second openings 42 a, 42 b exposespecific areas of the second sensing element 32′ and form the secondexposed sensing areas 32 a, 32 b, and the third opening 43 exposed aspecific area of the third sensing element 33′ and form the thirdexposed sensing area 33. The dimension of each of the exposed sensingareas is shown in FIG. 23.

Specifically, the first exposed sensing areas 31 a-31 d, the secondexposed areas 32 a, 32 b and the third exposed sensing area 33 aredivided into a plurality of coding areas. The width W4 of the parallellight or near-parallel light P is smaller than or equal to the width ofeach of the coding areas. Referring to FIG. 23, the first exposedsensing areas 31 a-31 d, the second exposed sensing areas 32 a, 32 b andthe third exposed sensing area 33 respectively include four, two and onecoding areas each having a width of ⅛ D2.

In the present embodiment, the width W4 of the parallel light ornear-parallel light P is smaller or equal to ⅛ of the width D4 of theoptical sensing module 3, i.e., W4≤⅛ D4. As mentioned in the previousembodiments, the width of each of the aspherical projections 1020 isequal to the width D4 of the optical sensing module 3. For example, inthe state shown in FIG. 23, the parallel light or near-parallel light Pprojects onto the optical sensing module 3 and allows the opticalsensing module 3 to generate a signal of [0,0,0]. In the fourthembodiment, the signals generated by the optical sensing module 3 inaccordance with the rotation position of the light-guiding grating wheel1 are shown in FIG. 24. In the fourth embodiment, the optical scanninglight-guiding encoder E can generate 2³=8 signals.

In sum, the advantage of the instant disclosure is that the scanninglight-guiding encoder by forward focusing E employs the design of “eachof the sensor elements has an exposed sensing area, and the plurality ofexposed sensing areas of the plurality of sensor elements are offset inthe transverse direction and are arranged along a plurality of differenthorizontal lines parallel to each other”, and hence, the parallel lightor near parallel light P projected onto the optical sensing module 3 cancooperate with the exposed sensing areas of the plurality of sensorelements. Therefore, the resolution of the encoder can be improvedwithout increasing the dimension of the light-guiding grating wheel 1and the number of the aspherical projections 1020. In addition, theoptical scanning light-guiding encoder by forward focusing E can achieveadjustable width of the parallel light or the near-parallel light P byadjusting the curvature of a top curved surface of the asphericalprojections 1020, or by setting the width of each of the asphericalprojections 1020 of the light-guiding body 101 same as the width of theoptical sensing module 3 for further improving the resolution of theoptical scanning light-guiding encoder by forward focusing E.

The above-mentioned descriptions represent merely the exemplaryembodiment of the present disclosure, without any intention to limit thescope of the instant disclosure thereto. Various equivalent changes,alterations or modifications based on the claims of the instantdisclosure are all consequently viewed as being embraced by the scope ofthe instant disclosure.

What is claimed is:
 1. A scanning light-guiding encoder, comprising: a light-guiding grating wheel including a light-guiding body and an outer gear-like structure disposed on an outer surrounding surface of the light-guiding body; a light-emitting module surrounded by the light-guiding grating wheel; an optical sensor module including a plurality of sensor elements adjacent to the light-guiding grating wheel, each of the plurality of sensor elements having an exposed sensing area, each of the exposed sensing areas being offset from and being arranged parallel to another adjacent exposed sensing area; and a grating disposed between the light-guiding grating wheel and the optical sensor module, the grating includes a plurality of slits for exposing the plurality of exposed sensing areas.
 2. The scanning light-guiding encoder according to claim 1, wherein each of the slits is offset from another adjacent slit.
 3. The scanning light-guiding encoder according to claim 1, wherein the light-guiding body having an inner surrounding surface which is an annular light-receiving surface, the outer gear-like structure having an annular light-output surface formed by a plurality of spherical or aspherical surfaces connected sequentially and having a principal axis, and the outer gear-like structure being formed by a plurality of aspherical projections connected sequentially, wherein an incident light generated by the light-emitting module enters the light-guiding grating wheel through the annular light-receiving surface and passes through the annular light-output surface of the outer gear-like structure for forming a plurality of rays of light parallel or near parallel to each other that are projected onto the optical sensor module.
 4. The scanning light-guiding encoder according to claim 1, wherein the light-guiding grating wheel includes an inner gear-like structure disposed on an inner surrounding surface of the light-guiding body, and the light-guiding body having an outer surrounding surface which is an annular light-output surface, the inner gear-like structure having an annular light-incident surface formed by a plurality of spherical or aspherical surfaces connected sequentially and having a principal axis, and the inner gear-like structure is formed by a plurality of aspherical projections connected sequentially, wherein an incident light generated by the light-emitting module enters the light-guiding grating wheel through the annular light-incident surface of the inner gear-like structure and passes through the annular light-output surface for forming a plurality of light parallel or near parallel to each other that are projected onto the optical sensor module.
 5. The scanning light-guiding encoder according to claim 1, wherein the light-guiding grating wheel includes an inner gear-like structure disposed on an inner surrounding surface of the light-guiding body, and the outer gear-like structure having an annular light-output surface formed by a plurality of spherical or aspherical surfaces connected sequentially and having a principal axis, the outer gear-like structure being formed by a plurality of aspherical projections connected sequentially, the inner gear-like structure having an annular light-receiving surface formed by a plurality of spherical or aspherical surfaces connected sequentially and having a principal axis, and the inner gear-like structure being formed by a plurality of aspherical projections connected sequentially, wherein an incident light generated by the light-emitting module enters the light-guiding grating wheel through the annular light-receiving surface of the inner gear-like structure and passes through the annular light-output surface of the outer gear-like structure for forming a plurality of rays of light parallel or near parallel to each other that are projected onto the optical sensor module.
 6. The scanning light-guiding encoder according to claim 1, wherein the light-guiding grating wheel has a plurality of aspherical projections, each of the aspherical projections having an aspherical surface, when the light-guiding grating wheel rotates, an incident light generated by the light-emitting module passes through a part of the plurality of aspherical surfaces or is reflected by the other part of the plurality of aspherical surfaces.
 7. The scanning light-guiding encoder according to claim 6, wherein each of the aspherical surfaces of the light-guiding grating is formed by two reflecting surfaces and a light-output surface connected between the two reflecting surfaces.
 8. The scanning light-guiding encoder according to claim 7, wherein when the light-guiding grating wheel rotates, a part of the incident light passes through the light-output surface.
 9. The scanning light-guiding encoder according to claim 7, wherein a part of the incident light is reflected by the reflecting surfaces.
 10. The scanning light-guiding encoder according to claim 7, wherein a parallel or near parallel rays of light have a width equal to a width of the light-output surface.
 11. The scanning light-guiding encoder according to claim 6, wherein each of the exposed sensing areas of the sensor elements is divided into a plurality of subareas, and a width of parallel or near parallel light formed by a plurality of rays of light parallel or near parallel to each other is not greater than a width of each of the plurality of subareas.
 12. A scanning light-guiding encoder, comprising: a light-guiding grating wheel including a light-guiding body and a gear-like structure, wherein the gear-like structure has a plurality of aspherical projections; a light-emitting module surrounded by the light-guiding grating wheel; an optical sensing module adjacent to the light-guiding grating wheel; and a grating disposed between the light-guiding grating wheel and the optical sensor module, the grating includes a plurality of slits extending straight and being offset from each other; wherein an incident light generated by the light-emitting module passes through the light-guiding grating wheel for forming parallel or near parallel light formed by a plurality of rays of light parallel or near parallel to each other and projected onto the optical sensing module and wherein a curvature of a top curved surface of each of the aspherical projections correlates to a width of the parallel near parallel light.
 13. A scanning light-guiding encoder, comprising: a light-guiding grating wheel including a light-guiding body and a gear-like structure, wherein the gear-like structure has a plurality of projections; a light-emitting module surrounded by the light-guiding grating wheel; an optical sensing module adjacent to the light-guiding grating wheel; and a grating disposed between the light-guiding grating wheel and the optical sensor module, the grating includes a plurality of slits extending straight and being offset from each other; wherein a width of each of the projections of the gear-like structure is equal to a width of the optical sensing module.
 14. The scanning light-guiding encoder according to claim 13, wherein the projections are aspherical projections or spherical projections.
 15. The scanning light-guiding encoder according to claim 2, wherein each of the slits is rectangular.
 16. The scanning light-guiding encoder according to claim 2, wherein an area of each of the slits is equal to and overlaps completely with an area of a corresponding one of the exposed sensing areas. 